U.S. patent application number 12/598995 was filed with the patent office on 2010-06-10 for construction machine.
This patent application is currently assigned to Hitachi Construction Machinery Co., Ltd.. Invention is credited to Yasushi Arai, Shohei Kamiya, Kazunori Nakamura.
Application Number | 20100139255 12/598995 |
Document ID | / |
Family ID | 40075069 |
Filed Date | 2010-06-10 |
United States Patent
Application |
20100139255 |
Kind Code |
A1 |
Kamiya; Shohei ; et
al. |
June 10, 2010 |
Construction Machine
Abstract
[PROBLEM] To provide a construction machine capable of
performing necessary operation or operations without a difficulty
even when a remaining amount of a reducing agent becomes small.
[SOLUTION] In a hydraulic excavator having an engine, a hydraulic
cylinder (18), plural actuators including a hydraulic motor (29),
and an exhaust gas treatment system for subjecting, to purification
treatment, nitrogen oxides in exhaust gas from the engine, the
hydraulic excavator is provided with an actuator operation control
means for performing, when the remaining amount of the reducing
agent in a reducing agent storage tank (30) is detected by a
remaining reducing-agent amount detector (33) to have become equal
to or smaller than a predetermined remaining amount, limiting
control to limit an operation of the hydraulic cylinder (18) such
that a front working implement driven by the hydraulic cylinder
(18) becomes difficult to exhibit its function, and at a same time,
holding control for holding the hydraulic motor (20) operable such
that a function of a travel base (1) or swing upperstructure (3)
driven by the hydraulic motor (20) can be exhibited.
Inventors: |
Kamiya; Shohei;
(Tsuchiura-shi, JP) ; Nakamura; Kazunori;
(Tsuchiura-shi, JP) ; Arai; Yasushi;
(Tsuchiura-shi, JP) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Hitachi Construction Machinery Co.,
Ltd.
Bunkyo-ku, Tokyo
JP
|
Family ID: |
40075069 |
Appl. No.: |
12/598995 |
Filed: |
May 28, 2008 |
PCT Filed: |
May 28, 2008 |
PCT NO: |
PCT/JP2008/059779 |
371 Date: |
November 5, 2009 |
Current U.S.
Class: |
60/287 ; 60/301;
60/303 |
Current CPC
Class: |
E02F 9/0808 20130101;
E02F 9/2246 20130101; F01N 2610/02 20130101; Y02T 10/12 20130101;
F01N 3/2066 20130101; E02F 9/00 20130101; Y02T 10/24 20130101; B01D
2251/2067 20130101; F01N 2900/1814 20130101; E02F 9/2203
20130101 |
Class at
Publication: |
60/287 ; 60/301;
60/303 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/10 20060101 F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2007 |
JP |
2007-145364 |
Claims
1. A construction machine having: an engine, a power source
drivable by the engine, and plural actuators drivable by power fed
from the power source, said actuators including a predetermined
actuator, and an exhaust gas treatment system arranged in an
exhaust passage from the engine, and comprising a reduction
catalyst for reducing and purifying nitrogen oxides in exhaust gas
with the reducing agent, a reducing agent storage tank, and a
remaining reducing-agent amount detector for detecting a remaining
amount of the reducing agent stored in the reducing agent storage
tank, characterized in that: the construction machine is provided
with an actuator operation control means for performing, when the
remaining amount of the reducing agent in the reducing agent
storage tank is detected by the remaining reducing-agent amount
detector to have become equal to or smaller than a predetermined
remaining amount, limiting control to limit an operation of the
predetermined actuator such that a load driven by the predetermined
actuator becomes difficult to exhibit a function thereof, and at a
same time, holding control for holding the at least one other
actuator, which is different from the predetermined actuator,
operable such that a function of another load driven by the at
least one other actuator can be exhibited.
2. The invention as defined in claim 1, wherein the limiting
control performed by the actuator operation control means is
control that inhibits the operation of the predetermined
actuator.
3. The invention as defined in claim 1, wherein the holding control
performed by the actuator operation control means is control that
enables an operation of the at least one other actuator at a normal
speed free from any speed limitation to the at least one other
actuator.
4. The invention as defined in claim 1, wherein: the at least one
other actuator is the travel actuator or swing actuator, and the
predetermined actuator is an actuator different from the travel
actuator or swing actuator.
5. The invention as defined in claim 4, wherein: the construction
machine is a hydraulic excavator, and the predetermined actuator is
an actuator for driving a front working implement.
6. The invention as defined in claim 2, wherein: the at least one
other actuator is the travel actuator or swing actuator, and the
predetermined actuator is an actuator different from the travel
actuator or swing actuator.
7. The invention as defined in claim 3, wherein: the at least one
other actuator is the travel actuator or swing actuator, and the
predetermined actuator is an actuator different from the travel
actuator or swing actuator.
Description
TECHNICAL FIELD
[0001] This invention relates to a construction machine such as a
hydraulic excavator, which is provided with an exhaust gas
treatment system having a reduction catalyst for decreasing NOx in
exhaust gas from an engine.
BACKGROUND ART
[0002] As a result of the application of higher-order emission
control standards to diesel engines, it has become necessary
nowadays to install an exhaust gas treatment system in addition to
a muffler on a vehicle body on which an engine is mounted. Examples
of the above-mentioned exhaust gas treatment system include
particulate matter trap filters, NOx treatment systems of the
urea-selective reduction type, NOx catalysts, and the like. It is
an NOx treatment system of the urea-selective reduction type that
uses a liquid reducing agent for such reduction of NOx and the
liquid reducing agent is an aqueous urea solution.
[0003] As a conventional technology of this sort, there is the
technology described in Patent Document 1. In an exhaust gas
treatment system according to this conventional technology, an
oxidation catalyst, an NOx storage catalyst and a selective
reducing-agent catalyst are arranged in an exhaust passage of an
internal combustion engine. Further, the exhaust gas treatment
system is provided with a reducing agent injection device for
injecting a reducing agent, i.e., an aqueous urea solution, which
is fed from an aqueous urea solution tank as a reducing agent
storage tank, into the exhaust passage, that is, an injection
nozzle, and also, with a remaining reducing-agent amount detection
device for detecting a remaining amount of the aqueous urea
solution in the aqueous urea solution tank, that is, an aqueous
urea solution sensor.
[0004] This conventional technology is designed such that, when the
remaining amount of the aqueous urea solution in the aqueous urea
solution tank as detected by the aqueous urea solution sensor has
become small, control is performed to reduce an output torque or
the like and hence to lower the concentration of NOx in exhaust
gas, thereby allowing the vehicle to reach a service station, where
the aqueous urea solution can be replenished, while limiting the
degree of decrease of the aqueous urea solution in the aqueous urea
solution tank.
Patent Document 1: JP-A-2006-226171
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0005] In a construction machine to which the present invention can
be applied, such as a hydraulic excavator, the performance of
control to reduce an output torque as in the above-described
conventional technology when the remaining amount of an aqueous
urea solution, that is, a reducing agent has become equal to or
smaller than a predetermined remaining amount results in a
situation that the operating speed of a working actuator for
driving a load such as a front working implement becomes slower and
the operating speeds of a travel actuator and swing actuator also
become slower. Namely, the operating speeds of all the actuators
become slower, so that motions of a load, such as the front working
implement, and other loads, such as a travel base and swing
upperstructure, become slow. There is, accordingly, such a concern
that it may take time in traveling to a replenishment place for the
reducing agent or a trouble may arise in connection with such an
operation as needed to quickly perform a travel or swing for the
avoidance of a danger in the event of an emergency.
[0006] The present invention has been completed in view of the
current situation of the above-mentioned conventional technology,
and its object is to provide a construction machine capable of
performing a necessary operation without a difficulty even when the
remaining amount of a reducing agent has become small.
Means for Solving the Problems
[0007] To achieve this object, the present invention is
characterized in that in a construction machine having an engine, a
power source drivable by the engine, and plural actuators drivable
by power fed from the power source, said actuators including a
predetermined actuator, and also an exhaust gas treatment system
arranged in an exhaust passage from the engine, and comprising a
reduction catalyst for reducing and purifying nitrogen oxides in
exhaust gas with the reducing agent, a reducing agent storage tank,
and a remaining reducing-agent amount detector for detecting a
remaining amount of the reducing agent stored in the reducing agent
storage tank, the construction machine is provided with an actuator
operation control means for performing, when the remaining amount
of the reducing agent in the reducing agent storage tank is
detected by the remaining reducing-agent amount detector to have
become equal to or smaller than a predetermined remaining amount,
limiting control to limit an operation of the predetermined
actuator such that a load driven by the predetermined actuator
becomes difficult to exhibit a function thereof, and at a same
time, holding control for holding at least one other actuator,
which is different from the predetermined actuator, operable such
that a function of another load driven by the at least one other
actuator can be exhibited.
[0008] To enable an operation for replenishing the reducing agent
or a necessary operation such as a quick operation for the
avoidance of a danger in the event of an emergency even when the
remaining amount of the reducing agent in the reducing agent
storage tank has become small, the present invention constituted as
descried above performs advance selection of an actuator, which can
be considered to be kept inoperative under such a situation, as the
predetermined actuator, and also advance selection of at least one
other actuator, an operation of which is considered to be needed
under such a situation, as the remaining actuators. When the
remaining amount of the reducing agent in the reducing agent
storage tank is detected by the remaining reducing-agent amount
detector to have become equal to or smaller than the predetermined
remaining amount in the above-described situation, the limiting
control is performed by the actuator operation control means to
limit the operation of the predetermined actuator so that the
exhibition of the function of the load driven by the predetermined
actuator is inhibited, and on the other hand, the holding control
is performed by the actuator operation control means to hold the at
least one other actuator operable such that the function of the
another load driven by the at least one other actuator can be
exhibited.
[0009] As described above, when the remaining amount of the
reducing agent in the reducing agent storage tank has become equal
to or smaller than the predetermined remaining amount, the
operation of the predetermined actuator is limited under the
limiting control by the actuator operation control means to reduce
the load on the engine, thereby making it possible to lower the
concentration of NOx in exhaust gas. As a consequence, the degree
of decrease of the reducing agent in the reducing agent storage
tank can be limited.
[0010] The operation of the predetermined actuator is limited as
described above, and as a result, the motion of the load driven by
the predetermined actuator is limited. This can make the operator
of the construction machine become aware that the remaining amount
of the reducing agent in the reducing agent storage tank is equal
to or smaller than the predetermined remaining amount and the
reducing agent needs to be replenished.
[0011] In particular, even when the remaining amount of the
reducing agent in the reducing agent storage tank has become equal
to or smaller than the predetermined remaining amount, it is still
possible, as described above, to drive the another load by an
operation of the at least one other actuator and hence to perform a
necessary operation without a difficulty.
[0012] The present invention is also characterized in that in the
above-described invention, the limiting control performed by the
actuator operation control means is control that inhibits the
operation of the predetermined actuator.
[0013] According to the present invention constituted as described
above, the drive of the load associated with the predetermined
actuator is stopped under the limiting control by the actuator
operation control means when the remaining amount of the reducing
agent in the reducing agent storage tank has become equal to or
smaller than the predetermined remaining amount. As a consequence,
the load on the engine can be reduced more certainly. Further, it
is possible to make the operator become aware more clearly that the
remaining amount of the reducing agent in the reducing agent
storage tank is small and the reducing agent needs to be
replenished.
[0014] The present invention is further characterized in that in
the above-described invention, the holding control performed by the
actuator operation control means is control that enables an
operation of the at least one other actuator at a normal speed free
from any speed limitation to the at least one other actuator.
[0015] According to the present invention constituted as described
above, the at least one other actuator can still be operated at the
normal speed to perform the necessary operation more certainly
under the holding control by the actuator operation limiting means
even when the remaining amount of the reducing agent in the
reducing agent storage tank has become equal to or smaller than the
predetermined remaining amount.
[0016] The present invention is still further characterized in that
in the above-described invention, the at least one other actuator
is the travel actuator or swing actuator and the predetermined
actuator is an actuator different from the travel actuator or swing
actuator.
[0017] According to the present invention constituted as described
above, it is still possible to perform a travel operation by the
operation of the travel actuator and/or a swing operation by the
swing actuator even when the remaining amount of the reducing agent
in the reducing agent storage tank has become equal to or smaller
than the predetermined remaining amount. Therefore, it is possible
to promptly perform a replenishing operation of the reducing agent
by the travel operation or an avoidance maneuver in the event of an
emergency by the travel operation and/or swing operation.
[0018] The present invention is even still further characterized in
that in the above-described invention, the construction machine is
a hydraulic excavator and the predetermined actuator is an actuator
for driving a front working implement.
[0019] According to the present invention constituted as described
above, the motion of the front working implement is limited under
the limiting control by the actuator operation limiting means when
the remaining amount of the reducing agent in the reducing agent
storage tank has become equal to or smaller than the predetermined
remaining amount. By the limited motion of the front working
implement, it is, therefore, possible to make the operator of the
hydraulic excavator become aware that the remaining amount of the
reducing agent in the reducing agent storage tank is small and the
reducing agent needs to be replenished.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0020] To enable a necessary operation even when the reducing agent
has become small, the present invention beforehand selects an
actuator, which can be considered to be kept inoperative under such
a situation, as a predetermined actuator, and also beforehand
selects at least one other actuator, an operation of which is
considered be needed under such a situation, as an actuator
different from the predetermined actuator. When the remaining
amount of the reducing agent has become equal to or smaller than
the predetermined remaining amount, the motion of the load driven
by the predetermined actuator is limited under limiting control of
the predetermined actuator by the actuator operation control means.
By this limited motion of the load, it is possible to make the
operator of the construction machine become aware that the reducing
agent needs to be replenished. Further, when the remaining amount
of the reducing agent has become equal to or smaller than the
predetermined remaining amount as described above, the limiting
control of the predetermined actuator can reduce the load on the
engine, thereby making it possible to lower the concentration of
NOx in exhaust gas and hence to limit the degree of decrease of the
reducing agent in the reducing agent storage tank. In particular,
even in a situation that the remaining amount of the reducing agent
has become equal to or smaller than the predetermined remaining
amount, the operating speed of the at least one other actuator can
be held so that the another load associated with the at least one
other actuator can be quickly moved. It is, therefore, possible to
perform without a difficulty a necessary operation such as an
operation for the replenishment of the reducing agent or an
operation for the avoidance of a danger in the event of an
emergency. The construction machine can, therefore, be provided
with higher reliability than conventional construction
machines.
BEST MODE FOR CARRYING OUT THE INVENTION
[0021] The present invention will hereinafter be described based on
a best mode for carrying out the construction machine according to
the present invention.
[0022] FIG. 1 is a side view showing a hydraulic excavator
according to one embodiment of the construction machine of the
present invention, FIG. 2 is a diagram depicting a drive circuit
and exhaust gas treatment system arranged in the embodiment, and
FIG. 3 is a flow chart illustrating essential parts of processing
executed at a controller included in the drive circuit arranged in
the embodiment.
[0023] As shown in FIG. 1, this embodiment is provided with a
travel base 1 having tracks drivable by a travel actuator, for
example, a travel motor 2, and a swing upperstructure 3 disposed on
the travel base 1 and drivable by an unillustrated swing actuator,
for example, a swing motor. An operator's cab 4 is arranged on the
swing upperstructure 3 at a forward position thereof. At a position
rear of the operator's cab 4, an engine compartment 5 is arranged
with an engine 6 accommodated therein, and on a rear end portion, a
counterweight 7 for ensuring weight balancing is arranged.
[0024] This embodiment is provided, on a forward side of the swing
upperstructure 5, with a boom 8 mounted pivotally in an up-and-down
direction on the swing upperstructure 5, an arm 9 secured pivotally
in an up-and-down direction on a free end of the boom 8, and a
bucket 10 attached pivotally in an up-and-down direction on a free
end of the arm 9. This embodiment is also provided with a boom
cylinder 11 for driving the boom 8, an arm cylinder 12 for driving
the arm 9, and a bucket cylinder 13 for driving the bucket 10. A
front working implement, which can perform digging work and the
like, is constructed by these boom 8, arm 9, bucket 10, boom
cylinder 11, arm cylinder 12 and bucket cylinder 13.
[0025] As depicted in FIG. 2, this embodiment is also provided with
main hydraulic pumps 14,15 and pilot hydraulic pumps 16,17, which
are drivable by the engine 6 and make up power sources. In FIG. 2,
a hydraulic cylinder 18 which constitutes a hydraulic actuator
exemplifies the above-mentioned boom cylinder 11, arm cylinder 12
or bucket cylinder 13. On the other hand, a hydraulic motor 20
exemplifies the above-mentioned travel motor 2 or swing motor.
[0026] The above-mentioned front working implement makes up a load
drivable by the hydraulic cylinder 18, while the above-mentioned
travel base 1 or swing upperstructure 3 makes up another load
drivable by the hydraulic motor 20. It is to be noted that, to
enable an necessary operation of the above-mentioned hydraulic
cylinder 18 even when a reducing agent in a reducing agent storage
tank 30 has become equal to or smaller than a predetermined
remaining amount, the hydraulic cylinder 18 has been selected
beforehand as a predetermined actuator which can be considered to
be kept inoperative under such a situation while the hydraulic
motor 20 has been selected beforehand as another actuator an
operation of which is considered be needed under such a
situation.
[0027] This embodiment is also provided with a first directional
control valve 19 arranged between the main hydraulic pump 14 and
the hydraulic cylinder 18 to control a flow of pressure oil to be
fed from the main hydraulic pump 14 to the hydraulic cylinder 18, a
second directional control valve 21 arranged between the main
hydraulic pump 15 and the hydraulic motor 20 to control a flow of
pressure oil to be fed from the main hydraulic pump 15 to the
hydraulic motor 20, a first control device 22 for generating a
secondary pressure, which is adapted to switch the first
directional control valve 19, as a signal pressure by using as a
primary pressure a pilot pressure delivered from the pilot
hydraulic pump 16, and a second control device 23 for generating a
secondary pressure, which is adapted to switch the second
directional control valve 21, as a signal pressure by using as a
primary pressure a pilot pressure delivered from the pilot
hydraulic pump 17. The above-described respective elements make up
the drive circuit arranged in this embodiment.
[0028] This embodiment is also provided with the exhaust gas
treatment system for decreasing nitrogen oxides, i.e., NOx in
exhaust gas from the engine 6. As depicted in FIG. 2, this exhaust
gas treatment system includes a reduction catalyst 29 arranged in
an exhaust passage 28 of the engine 6 to reduce and purify NOx in
exhaust gas with a reducing agent such as an aqueous urea solution,
the reducing agent storage tank 30 for storing the reducing agent
such as the aqueous urea solution, and a remaining reducing-agent
amount detector 33 for detecting a remaining amount of the reducing
agent stored in the reducing agent storage tank 30. The exhaust gas
treatment system also includes a reducing agent feeder 31 for
drawing in the reducing agent from the reducing agent remaining
amount storage tank 30, in which the reducing agent is stored, and
feeding the same, and a reducing agent injector 32 for injecting
the reducing agent, which has been fed by the reducing agent feeder
31, into the exhaust passage 28 at a location on an upstream side
of the reduction catalyst 29.
[0029] This embodiment is also provided with a first signal path 24
for guiding a signal pressure which is to be fed from the first
control device 22 to a control port of the first directional
control valve 19, a first signal control device 25 composed, for
example, of an on/off valve capable of cutting off or communicating
the first signal path 24, a second signal path 26 for guiding a
signal pressure which is to be fed from the second control device
23 to a control port of the second directional control valve 21,
and a second signal control device 27 composed, for example, of an
on/off valve capable of cutting off or communicating the second
signal path 26. This embodiment is also provided with a controller
35 having a determination means for comparing the remaining amount
of the reducing agent as detected by the above-mentioned remaining
reducing-agent amount detector 33 with the predetermined remaining
amount set in advance and making a determination and adapted to
output, based on a result of the determination, control signals to
control the first signal control device 25 and second signal
control device 27, and a monitor 34 connected to the controller 35
and capable of displaying that the remaining amount of the reducing
agent is small. This monitor 34 is arranged, for example, in the
operator's cab 4.
[0030] The above-mentioned controller 35 and the above-mentioned
first signal control device 25 and second signal control device 27
make up an actuator operation control means that, when the
remaining amount of the reducing agent in the reducing agent
storage tank 30 is detected by the remaining reducing-agent amount
detector 33 to have become equal to or smaller than the
predetermined remaining amount, performs limiting control to limit
an operation of the hydraulic cylinder 18 as the predetermined
actuator such that the load driven by the hydraulic cylinder 18,
specifically the front working implement becomes difficult to
exhibit its function, and at a same time, holding control to enable
an operation of the hydraulic motor 20 as the at least one other
actuator different from the predetermined actuator such that the
function of another load driven by the hydraulic motor 20,
specifically the travel base 1 or swing upperstructure 3 is
exhibited.
[0031] The limiting control performed by the actuator operation
control means can be, for example, control that inhibits an
operation of the hydraulic cylinder 18, while the holding control
performed by the actuator operation control means can be, for
example, control that enables an operation of the hydraulic motor
20 at a normal speed free from any speed limitation to the
hydraulic motor 20.
[0032] In this embodiment constituted as described above, while the
reducing agent in the reducing agent storage tank 30 is detected by
the remaining reducing-agent amount detector 33 to be greater than
the predetermined remaining amount and to be in such a remaining
amount as requiring no replenishment, specifically when a
determination (remaining urea solution amount.ltoreq.predetermined
remaining amount?) by the determination means built in the
controller 35 as shown in step S1 of FIG. 3 is "NO", the first
signal control device 25 and second signal control device 27 hold
the first signal path 24 and second signal path 26 in communicated
states, respectively, by control signals outputted from the
controller 35 on the basis of the determination.
[0033] When, for example, the first control device 22 is operated
in the state that the first signal path 24 and second signal path
26 are held communicated as described above, a signal pressure
corresponding to the stroke of the operation of the first control
device 22 is applied to the control port of the first directional
control valve 19 via the first signal path 24 and first signal
control device 25, and the first directional control valve 19 is
switched. As a result, the pressure oil delivered from the main
hydraulic pump 14 is fed to the hydraulic cylinder 18 via the first
directional control valve 19, and hence, the hydraulic cylinder 18
is operated to drive the above-mentioned front working implement.
It is, therefore, possible to perform digging work or the like via
driving of the boom 8, arm 9 and bucket 10.
[0034] When, for example, the second control device 23 is operated
in the state that the first signal path 24 and second signal path
26 are held communicated, a signal pressure corresponding to the
stroke of the operation of the second control device 23 is applied
to the control port of the second directional control valve 21 via
the second signal path 26 and second signal control device 27, and
the second directional control valve 21 is switched. As a result,
the pressure oil delivered from the main hydraulic pump 15 is fed
to the hydraulic motor 20 via the second directional control valve
21, and hence, the hydraulic motor 20 is operated to drive the
travel base 1 or swing upperstructure. It is, therefore, possible
to perform a combined operation of front work and travel, a single
travel operation, a single swing operation, or the like.
[0035] During the above-mentioned drive of the front working
implement or the above-mentioned travel operation or swing
operation, the reducing agent which has been drawn in by the
reducing agent feeder 31 from the reducing agent storage tank 30 is
fed to the reducing agent injector 32, and is then injected from
the reducing agent injector 32 into the exhaust passage 28 of the
engine 6. Exhaust gas, in which the reducing agent has been
incorporated as described above, comes into contact with the
reduction catalyst 29 arranged in the exhaust passage 28, whereby
NOx in the exhaust gas are degreased as is known well.
[0036] On the other hand, when the remaining amount of the reducing
agent in the reducing-agent storage tank 30 is detected by the
remaining reducing agent amount detector 33 to be smaller than the
predetermined remaining amount and to be a remaining amount that
needs to be replenished, specifically when the determination
(remaining urea solution amount.ltoreq.predetermined remaining
amount?) by the determination means built in the controller 35 as
shown in step S2 of FIG. 3 is "YES", a display signal is outputted
from the controller 35 to the monitor 34, and a warning is
displayed on the monitor 34 to the effect that the remaining amount
of the reducing agent is small and a replenishment is needed. In
addition, the actuator operation control means as an element
characteristic to this embodiment is actuated to perform limiting
control that the first signal control device 25 cuts off the first
signal path 24 by a control signal from the controller 35,
specifically limiting control that inhibits an operation of the
hydraulic cylinder 18 which drives the front working implement, and
also holding control that the second signal control device 27 still
holds the second signal path 26 in the communicated state,
specifically holding control that enables an operation of the
hydraulic motor 20, which drives the travel base 1 or swing
upperstructure 3, at the normal speed free from any speed
limitation to the hydraulic motor 20. As a consequence, the front
working implement is held in a drive stopped state that its
function cannot be exhibited, and the travel base 1 and swing
upperstructure 2 are held in states that their functions can be
exhibited.
[0037] Described specifically, even when the first control device
22 is operated, a signal pressure generated at the first control
device 22 is cut off at the first signal control device 25 and is
not guided to the control port of the first directional control
valve 19, so that the first directional control valve 19 is held in
a neutral position. Therefore, the pressure oil from the main
hydraulic pump 14 is not fed to the hydraulic cylinder 18, and the
front working implement is held in the drive stopped state. When
the second control device 23 is operated, a signal pressure
corresponding to the stroke of the operation of the second control
device 23 is applied to the control port of the second directional
control valve 21 via the second signal path 26 and second signal
control device 27, and the second directional control valve 21 is
switched, as mentioned above. As a result, the pressure oil
delivered from the main hydraulic pump 15 is fed to the hydraulic
motor 20, and the hydraulic motor 20 is operated to enable driving
of the travel base 1 or swing upperstructure 3.
[0038] In this embodiment constituted as described above, when the
remaining amount of the reducing agent in the reducing agent
storage tank 30 has become equal to or smaller than the
predetermined remaining amount, an operation of the hydraulic
cylinder 18 is inhibited under limiting control by the actuator
operation control means including the determination means built in
the controller 35, and the front working implement is held in the
drive stopped state. Therefore, the load on the engine 6 is
reduced, and the concentration of NOx in exhaust gas flowing
through the exhaust passage 28 can be lowered. As a consequence,
the degree of decrease of the reducing agent in the reducing agent
storage tank 30 can be limited.
[0039] The display of the warning on the monitor 34 can make the
operator of the hydraulic excavator become aware that the remaining
amount of the reducing agent in the reducing agent storage tank 30
is equal to or smaller than the predetermined remaining amount and
the reducing agent needs to be replenished. In addition, the
operation of the hydraulic cylinder 18 is inhibited, and as a
result, the motion of the front working implement driven by the
hydraulic cylinder 18 is stopped. This stoppage can also make the
operator of the hydraulic excavator become aware that the remaining
amount of the reducing agent in the reducing agent storage tank 30
is equal to or smaller than the predetermined remaining amount and
the reducing agent needs to be replenished.
[0040] In particular, even when the remaining amount of the
reducing agent in the reducing agent storage tank 30 has become
equal to or smaller than the predetermined remaining amount as
descried above, the travel base 1 or swing upperstructure 3 can be
quickly moved by an operation of the hydraulic motor 20 so that a
necessary motion, specifically a travel operation or swing
operation can still be performed. It is, therefore, possible to
perform without a difficulty a travel operation at a normal speed
for the replenishment of the reducing agent or a quick travel
operation or swing operation for the avoidance of a danger in the
event of an emergency. As a consequence, the construction machine
can be provided with high reliability.
[0041] The above-described embodiment is designed to have a
construction that the first signal control device 25 and second
signal control device 27 are both composed of on/off valves.
However, the embodiment may be designed to have a construction that
the first signal control device 25 is composed of a pressure
control valve and the second signal control device 27 is composed
of an on/off valve, a construction that the first signal control
device 25 is composed of an on/off valve and the second signal
control device 27 is composed of a pressure control valve, or a
construction that the first signal control device 25 and second
signal control device 27 are both composed of pressure control
valves.
[0042] A description will be made of the case that the embodiment
is designed to have the construction that the first signal control
device 25 is composed of the pressure control valve and the second
signal control device 27 is composed of the on/off valve. When the
remaining amount of the reducing agent in the reducing agent
storage tank 30 has become equal to or smaller than the
predetermined remaining amount, it becomes possible to output a
control signal from the controller 35 to the first signal control
device 25 such that the opening area of the first signal control
device 25 is controlled to permit feeding to the control port of
the first directional control valve 19 a signal pressure capable of
switching the first directional control valve 19 such that the
pressure oil can be fed from the hydraulic pump 14 to the hydraulic
cylinder 18 at such a flow rate as allowing the front working
implement to undergo such an extremely slow movement as failing to
perform intended work. On the other hand, the second signal control
device 25 holds the second signal path 26 in the communicated state
even in such a situation. The hydraulic motor 20 can, therefore, be
operated at a normal speed, so that the travel base 1 or swing
upperstructure 3 can be driven to perform a necessary operation,
such as a replenishing operation of the reducing agent or an
operation for the avoidance of a danger in the event of an
emergency, without a difficulty.
[0043] A description will next be made of the case that the
embodiment is designed to have the construction that the first
signal control device 25 is composed of the on/off valve and the
second signal control device 27 is composed of the pressure control
valve. When the remaining amount of the reducing agent in the
reducing agent storage tank 30 has become equal to or smaller than
the predetermined remaining amount, the front working implement is
held in a drive stopped state, and at the same time, it becomes
possible to output a control signal from the controller 35 to the
second signal control device 27 such that the opening area of the
second signal control device 27 is controlled to feed to the
control port of the second directional control valve 21 a signal
pressure capable of switching the second directional control valve
21 such that the pressure oil can be fed from the main hydraulic
pump 15 to the main hydraulic motor 20, which drives the travel
base 1 or swing upperstructure 2, at such a flow rate as enabling a
travel operation or swing operation at a speed which is slower than
the normal speed but is still sufficiently fast. The embodiment
constituted as described above can also perform a necessary
operation without a difficulty in a situation that the remaining
amount of the reducing agent has become equal to or smaller than
the predetermined remaining amount, although the operation is
slower than that in the first embodiment.
[0044] A description will further be made of the case that the
embodiment is designed to have the construction that the first
signal control device 25 and second signal control device 27 are
both composed of the pressure control valves. In a situation that
the remaining amount of the reducing agent has become equal to or
smaller than the predetermined remaining amount, it is possible, as
is appreciated from the foregoing description, to perform such an
extremely slow movement of the front working implement as failing
to perform its intended work and a travel operation or swing
operation at a speed which is slower than the normal speed but is
still sufficiently fast. It is, therefore, possible to perform a
necessary operation, such as a replenishing operation of the
reducing agent or an operation for the avoidance of a danger in the
event of an emergency, without a difficulty.
[0045] The above-described embodiment is designed to have the
construction that the hydraulic cylinder 18 has been selected
beforehand as a predetermined actuator to which the limiting
control is applied and that the hydraulic motor 20 has been
selected beforehand as another actuator to which the holding
control is applied. The present invention is, however, not limited
to such a construction. In view of necessary operations which are
conceivable under the situation that the reducing agent in the
reducing agent storage tank 30 has become small, these
predetermined actuator and another actuator can be selected from
plural actuators as needed.
[0046] The above-described embodiment is a hydraulic excavator, but
the present invention is not limited to such a hydraulic excavator.
The present invention can be applied to various construction
machines which are each provided with an engine, an exhaust gas
treatment system and plural actuators.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 A side view showing a hydraulic excavator as one
embodiment of the construction machine according to the present
invention.
[0048] FIG. 2 A diagram depicting a drive circuit and exhaust gas
treatment system arranged in the embodiment.
[0049] FIG. 3 A flow chart illustrating essential parts of
processing executed at a controller included in the drive circuit
arranged in the embodiment.
LEGEND
[0050] 1 Travel base [0051] 2 Travel motor (travel actuator) [0052]
3 Swing upperstructure [0053] 6 Engine [0054] 8 Boom [0055] 9 Arm
[0056] 10 Bucket [0057] 11 Boom cylinder [0058] 12 Arm cylinder
[0059] 13 Bucket cylinder [0060] 14 Main hydraulic pump (power
source) [0061] 15 Main hydraulic pump (power source) [0062] 16
Pilot hydraulic pump (power source) [0063] 17 Pilot hydraulic pump
(power source) [0064] 18 Hydraulic cylinder (predetermined
actuator) [0065] 19 First directional control valve [0066] 20
Hydraulic motor (at least one other actuator) [0067] 21 Second
directional control valve [0068] 22 First control device [0069] 23
Second control device [0070] 24 First signal path [0071] 25 First
signal control device (actuator operation control means) [0072] 26
Second signal path [0073] 27 Second signal control device (actuator
operation control means) [0074] 28 Exhaust passage [0075] 29
Reduction catalyst [0076] 30 Reducing agent storage tank [0077] 33
Remaining reducing-agent amount detector [0078] 35 Controller
(actuator operation control means)
* * * * *